In 1991 the Centers for Disease Control and Prevention (CDC) lowered the blood lead (BPb) level of concern to 10 micrograms/dL, vastly increasing the number of children considered to have elevated BPb. Because inner- city pediatric practices have many children with BPb levels equal to or greater than 10 micrograms/dL, BPb testing and lead interventions occupy significant amounts of time and resources. Assessing the efficacy of intervention programs is therefore important. In order to determine the impact of interventions and which children to target for intervention, an understanding of the natural history of BPb levels is necessary. Scant information is available on the natural history of BPb levels <25 micrograms/dL. Once the natural history is known, an evaluation of lead intervention programs is possible. This study is designed to determine the natural history of BPb levels over one year among inner-city children, focusing on children receiving testing before the 1991 CDC statement lowered the BPb level of concern. This study will also evaluate the efficacy of intervention programs in place at these practices in 1992 to determine if lead intervention programs alter the natural history of BPb levels over one year. The large number of children with elevated BPb levels at these practices will allow for comparison of program effectiveness between the practices. Data will be gathered to describe differences in intervention intensity between programs. Data for this study will be collected via a retrospective medical record review of children having blood drawn for BPb level determination at three Chicago inner-city pediatric practices during defined enrollment periods before and after the CDC lowered the BPb level of concern. The practices that will be participating serve mainly black and Hispanic children, have been routinely testing BPb on young children for year. (30-40% of children have levels in excess of lO micrograms/dL), and have each developed intervention programs directed to parents of children with elevated BPb levels. A child's BPb level at the time of enrollment and a level 12 months later will be used to determine if the child's BPb is persistently high, persistently low, or transitional. Statistical comparisons of BPb between initial and 12 month level, between enrollment years, and between practices will include kappa, chi2, and analysis of variance. This study will determine the natural history of BPb levels and evaluate lead intervention programs at three inner-city pediatric practices, addressing an important health care need of minority children and establishing a foundation for future research. The detrimental impact of elevated BPb on neurocognitive and motor functioning and the time, expense, and difficulty of tracking children and educating families about BPb elevation make this an important research priority.